1. Field of the Invention
The present invention relates to controlling exposure control of a camera based on images captured by the camera, and in particular, to controlling the exposure of a camera mounted in a vehicle.
2. Description of the Related Art
A technology is known in which exposure control of a camera that is installed in a vehicle is performed based on an image captured by the camera. For example, JP-A-2010-041668 discloses a technology in which a camera captures an image at an initial exposure. An adaptive exposure is then set based on the image captured at the initial exposure.
Specifically, a plurality of areas for exposure control are set in advance in the image captured at the initial exposure. An average luminance is detected for each of the areas. For each area, whether or not the area is an area (unsuitable area) in which edge components are assumed to be undetectable is judged based on the average luminance of the area. The edge components are undetectable due to excessive or insufficient exposure. When judged that any of the areas is an unsuitable area, the exposure of the camera is set to the adaptive exposure. The adaptive exposure is based on the average luminance of the unsuitable area.
As described above, a technology is known in which exposure control of a camera is performed based on the average luminance of an area for exposure control that is set in advance in an image captured by the camera. However, the appropriate manner of determining the area for exposure control in the captured image may differ depending on travel conditions of the vehicle and the like.